(1) Field of the Invention
The present invention relates to a novel shaping dope composition comprising at least one cellulose derivative, at least one acrylonitrile polymer and a solvent capable of substantially dissolving these polymeric materials simultaneously therein. The invention also relates to novel composite fibers comprising a cellulose derivative and an acrylonitrile polymer, which are made from such dope composition and are excellent in the thermal dimensional stability and mechanical properties, in which the cellulose derivative is present in the form of a dispersed phase of fine fibers in a matrix of the acrylonitrile polymer.
(2) Description of the Prior Art
A dope comprising a cellulose derivative and an acrylonitrile polymer dissolved in a common solvent is known. It also is known that phase separation takes place in such dope. For example, Cates: J. Polymer Sci., 20, 155 (1966), Japanese Patent Publication No. 968/56 and Japanese Patent Publication No. 2,317/58 teach a dope comprising cellulose acetate and an acrylonitrile polymer dissolved in N,N-dimethylformamide or dimethylsulfoxide. Japanese Patent Publication No. 2,986/62 teaches a dope comprising cellulose acetate and an acrylonitrile polymer dissolved in a concentrated aqueous solution of an inorganic salt. It also is taught that these dopes can be used for formation of fibers. Furthermore, Japanese Patent Publication No. 4,023/58 discloses a dope composition formed by dissolving cyanoethyl cellulose and an acrylonitrile polymer in N,N-dimethylformamide and Japanese Patent Publication No. 14,029/64 teaches that phase separation takes place in dope compositions formed by dissolving a cellulose derivative such as mentioned above and an acrylonitrile polymer in a solvent.